1. Field of the Invention
The present invention relates generally to an electrical device such as a ballast for fluorescent lamps, and an electrical unit including an electrical device and a lamp diffuser.
2. Description of the Related Art
Ballasts for fluorescent lamps, conventionally made typically as electronic ballasts, are generally attached to fluorescent lamps by hand, for example, mounted in a lamp diffuser. To install one such electronic ballast, typically an elongated hole is punched out in the ballast housing so that the housing may be attached to the lamp diffuser using bolts and nuts or rivets which are routed through the elongated hole. The housing also includes a circuit board provided therein, the circuit board having as the terminal element typically a terminal with a plurality of terminal sites. Generally, it is necessary to ground the electronic ballast housing and the circuit board, and may be achieved using an electrically conductive connection between the electronic ballast housing and the lamp diffuser via a separate cable connection. In such a case, the circuit board is grounded using a terminal site provided thereon via the electronic ballast housing.
Another possibility of grounding the electronic ballast housing and the circuit board is to use toothed lock washers when the nuts are screwed to the mounting bolts, the washers reliably separating any oxide or enamel layer which may be present on the lamp diffuser bottom or on the side surface of the housing so as to ensure good electrical contact for grounding by the screw attachment itself. This type of mounting of an electrical ballast in a lamp diffuser is disadvantageous since it results in high manual installation cost and imprecision in the positioning of the individual terminal sites of the terminal relative to the electronic ballast housing and relative to the lamp diffuser. This leads especially to problems when wiring the fluorescent lamps, therefore connection of individual wires of one or more cables to the terminal sites is done using automatic installation machines. If the terminal sites are inaccurately positioned, misinsertions of individual wires in the terminal sites often occur. Consequently, in order to prevent such an occurrence, an optical pattern recognition system is used for recognizing and accordingly correcting the positional inaccuracies of the terminal sites. The use of one such optical pattern recognition system is however very complex and accordingly expensive.
Even if the electronic ballast housing is positioned relatively accurately by fusing one border of the elongated hole in the electronic ballast housing as a stop, and thus, as a local reference base, the positional accuracy of one terminal site at a time is determined by a plurality of tolerances such as the positional tolerance of the terminal sites on the terminal, the positional tolerance of the terminal on the circuit board, the positional tolerance of the circuit board in the electronic ballast housing, the positional tolerance of the attachment of the electronic ballast housing to the lamp diffuser, etc. The amounts of these tolerances in the least favorable case is accumulatively added to one another. In the worst case, local displacement of the individual terminal sites occurs and corresponds at least to half the distance between two adjacent terminal sites or even exceeds the distance so that in this case misinsertions are inevitable in the wiring of the fluorescent lamp by means of automatic installation machines.
An object of the present invention is to provide an electrical device such as a ballast device for fluorescent lamps, and an electrical unit including one such electrical device and a lamp diffuser, in which the individual terminal sites of the terminal have only low positional tolerance so that wiring is made possible with an automatic installation machine without the danger of misinsertions.
The electrical device in accordance with the present invention is achieved by providing a catch element having at least one leg for attaching a terminal to the housing. In particular, the at least one leg connects the catch element to the terminal, and also attaches the catch element to the electric ballast housing. Thus, in accordance with the present invention, the catch element acts essentially as an intermediate piece between the terminal and the electric ballast housing, preferably, the connection of the terminal to the catch element on the one hand and the connection of the catch element to the housing on the other always taking place using the same catch leg. In this regard, when the terminal is attached to the electric ballast housing, there is a single reference point, specifically the attachment site of the catch leg on the catch element. Thus, the chain of tolerances which accumulate in the worst case, i.e., the chain which is present in the prior art, is avoided so that the accuracy of the local position of the individual terminal sites of the terminal relative to the housing is enhanced.
According to an exemplary embodiment of the present invention, at least one side wall of the electric ballast housing has a recess and the catch leg of the catch element is locked therein. Preferably, in order to minimize the aforementioned location inaccuracies of the terminal sites, the process takes place such that the size of the recess in the side wall of the housing is exactly matched to the size of the area of the catch leg fitting into the recess, thereby, the catch leg which is locked in the recess has essentially no more play.
Generally the electric ballast housings include two side walls positioned opposite and in parallel to one another. In an exemplary embodiment of the present invention, the catch element has exactly two catch legs which are preferably likewise opposite parallel to one another and in the two side walls of the housing there is one recess each for receiving the two catch legs. The size of the recesses is preferably matched exactly to the size of the area of the catch leg fitting into the recesses so that ultimately the catch element locked in the housing essentially no longer has any play.
The terminal is attached to the catch element according to an embodiment of the invention using at least one catch leg, and in the case of two catch legs, each leg having one inner projection which extends laterally over either the bottom of the terminal which is typically formed by the circuit board, or another area of the terminal which is suitable for this purpose, such that the terminal locks. In order to attach the terminal in the catch element, it is thus necessary for the two catch legs to be able to deflect to the outside when the terminal is pressed into the catch element in order then to snap over the bottom of the catch element again as soon as the terminal has been inserted deeply enough into the catch element.
According to a preferred embodiment of the invention, the catch element has two side walls whereby each side wall includes two catch legs, and whereby the side walls are connected to one another on the front side of the catch element with the front wall. This is advantageous especially in that the circuit board which is connected to the terminal or to which the terminal is attached is not limited in this way by the size of the catch element and can clearly extend to the rear over the catch element. Preferably, the catch element is otherwise provided with a bottom. Finally, in the electrical device in accordance with the present invention, the catch element generally is composed of an electrical nonconductive material such as a plastic.
In a preferred embodiment of the electrical device in accordance with the present invention, at least one of the front wall and the bottom of the catch element is used as bottom insertion protection. This bottom insertion protection essentially leads to insulation being ensured between the terminal sites or the electrical conductors connected to the terminal sites even when a metal part such as a screw, is positioned between the terminal and the bottom or the side walls of the housing, or when the electrical line is detached from the terminal site. Moreover, insulation of the inner area of the housing can be included at the inside surface of the housing and the housing bottom by covering them with an electrically insulating film.
A electrical unit in accordance with the present invention unit includes an electrical device as described above, and a lamp diffuser having a bottom, whereby the bottom of the electrical unit is provided with a slot, the bottom of the lamp diffuser includes a catch clip locked in the slot. One especially advantageous embodiment of the electrical unit arises especially by the terminal being attached by means of the above described catch element in the housing. By having such a design, the side walls of the housing having the aforementioned recesses punched out and the slot has been punched out in the housing bottom preferably in a single punching process with a single punching tool. In this way, between the recesses in the side walls of the housing on the one hand and the slot in the housing bottom on the other the minimum possible spacing tolerances are achieved so that as a result, by fitted insertion and catching of the housing on the catch clip on the bottom of the lamp diffuser, optimum positioning of the housing with the terminal installed on the lamp diffuser is achieved with minimum local tolerances.
According to another preferred embodiment of the above described electrical unit, the catch clip and the lamp diffuser bottom are made as one piece. Preferably, the catch clip is partially punched out of the lamp diffuser bottom and is bent out. Accordingly, the catch clip is punched out of the lamp diffuser so that the punched-out area which is designed to form the catch clip can be bent out of the plane of the lamp diffuser bottom so that the catch clip preferably projects at an angle of 90xc2x0 relative to the lamp diffuser bottom. For catching purposes, the catch clip preferably has at least one elastic catch tongue which is easily bent out of the plane of the catch clip. When the catch clip is inserted into the slot provided in the housing bottom this area springs back into the plane of the catch clip so that the housing can be pushed onto the catch clip and prevents removal or sliding back of the housing in its fully slipped-on and thus locked state.
A electrical unit in accordance with the present invention includes an electrical device, such as an electrical device as previously described, and a lamp diffuser which is provided with a bottom, is otherwise detached from the above described means, whereby the lamp diffuser bottom has a upwardly protruding grounding barb of electrically conductive material and the grounding barb is connected to the ground connection of the terminal. As a result, simple and reliable grounding of the terminal, and with a corresponding connection of the terminal to the housing, also grounding of the housing, are achieved which is automatically accomplished when attaching the housing to the lamp diffuser.
One especially simple embodiment of the grounding barb arises by the grounding barb and the lamp diffuser bottom being made in one piece and the grounding barb being partially punched out of the lamp diffuser bottom and bent out. In doing so, the grounding barb can be laterally routed past the housing in order to come into contact with the terminal. One preferred embodiment is, however, characterized in that the grounding barb is electrically connected to the housing, especially to the housing bottom. Finally, another preferred embodiment of the unit in accordance with the present invention is characterized in that the grounding barb is routed electrically conductively through a recess provided in the housing bottom.